It has been demonstrated that CD8 positive CTLs recognize epitope peptides derived from tumor-associated antigens (TAAs) found on the major histocompatibility complex (MHC) class I molecule, and then kill the tumor cells. Since the discovery of the melanoma antigen (MAGE) family as the first example of TAAs, many other TAAs have been discovered through immunological approaches (NPL 1, Boon T, Int J Cancer 1993 May 8, 54(2): 177-80; NPL 2, Boon T & van der Bruggen P, J Exp Med 1996 Mar. 1, 183(3): 725-9). Some of these TAAs are currently undergoing clinical development as immunotherapeutic targets.
Favorable TAAs are indispensable for the proliferation and survival of cancer cells. The use of such TAAs as targets for immunotherapy may minimize the well-described risk of immune escape of cancer cells attributable to deletion, mutation, or down-regulation of TAAs as a consequence of therapeutically driven immune selection. Accordingly, the identification of new TAAs capable of inducing potent and specific anti-tumor immune responses warrants further development and the clinical investigation of peptide vaccination strategies for various types of cancer is ongoing (NPL 3, Harris C C, J Natl Cancer Inst 1996 Oct. 16, 88(20): 1442-55; NPL 4, Butterfield L H et al., Cancer Res 1999 Jul. 1, 59(13): 3134-42; NPL 5, Vissers J L et al., Cancer Res 1999 Nov. 1, 59(21): 5554-9; NPL 6, van der Burg S H et al., J Immunol 1996 May 1, 156(9): 3308-14; NPL 7, Tanaka F et al., Cancer Res 1997 Oct. 15, 57(20): 4465-8; NPL 8, Fujie T et al., Int J Cancer 1999 Jan. 18, 80(2): 169-72; NPL 9, Kikuchi M et al., Int J Cancer 1999 May 5, 81(3): 459-66; NPL 10, Oiso M et al., Int J Cancer 1999 May 5, 81(3): 387-94). To date, several clinical trials using these tumor-associated antigen derived peptides have been reported. Unfortunately, many of the current cancer vaccine trial have shown only a low objective response rate (NPL 11, Belli F et al., J Clin Oncol 2002 Oct. 15, 20(20): 4169-80; NPL 12, Coulie P G et al., Immunol Rev 2002 October, 188: 33-42; NPL 13, Rosenberg S A et al., Nat Med 2004 September, 10(9): 909-15). Accordingly, there remains a need for new TAAs as immunotherapeutic targets.
Epithelial cell transforming sequence 2 (ECT2) oncogene (GenBank Accession No. AY376439; e.g., SEQ ID No: 41) has been discovered from the transcripts identified as up-regulated in cancer. The ECT2 gene is specifically up-regulated in the tumor cells of various cancers, including, but not limited to, bladder cancer, breast cancer, cervical cancer, cholangiocellular carcinoma, chronic myeloid leukemia (CML), colorectal cancer, esophageal cancer, non-small cell lung cancer (NSCLC), lymphoma, pancreatic cancer, prostate cancer, renal carcinoma and small cell lung cancer (SCLC) and thus is of particular to the present invention (PTL 1, WO2007/013671; PTL 2, WO2008/102557; PTL 3, WO2010/007791). In particular, immunogenic peptides derived from ECT2 may find utility in selectively killing tumor cells that express such antigens.